After exploring an epic fantasy realm for years it seems only natural—especially in the down time between books—to want to know what exists beyond the borders of the story in lands only hinted at. George R. R. Martin’s Song of Ice and Fire series accomplishes this in a wonderfully classic way, portraying a world that gets cloudy at the edges and hints that “here be dragons” while also literally pointing out… here be dragons.

The release of The Lands of Ice and Fire map book in the fall of 2012 finally gave us a beautiful, clear, and official picture of “the known world” in the series. So let’s see if we can figure out how large the entire world is and what percentage of that is the Known World.

When the series first started, George R. R. Martin had envisioned the lands of Westeros as residing on a “super Earth,” a terrestrial planet with more mass than the Earth, more gravity, and a larger surface area. Martin hasn’t repeated this statement recently (in fact, I can no longer find the interview online in which he said that) leading one to think he was just thinking out loud and that this is not a hard and fast rule. Martin also had Jon Snow claim that Westeros was 10,000 leagues long in one of the early books, a number which the author himself has since debunked, so it seems that the distances and geography of the world haven’t actually been pinned down until recently.

Let’s begin, using a handy tape measure and the real size map of the Known World. (Which is, of course, hanging on my wall at home because OOH, PRETTY.)

In inches, the distance from the wall to the south coast of Dorne is a very convenient 12, making each inch equivalent to 250 miles. The Known World map is 2 feet and 11 inches wide, minus the ornamental borders, totaling 8750 miles from east to west and 5750 miles from north to south.

The next thing we need to do is decide where the equator is on Planet Westeros. For the purposes of the forthcoming measurements, I’ve chosen the former site of the city of Valyria as being right on the equator. The lands to the north and south of it are clearly equatorial desert, jungle, and savannah, and there’s a certain poetry to having Valyria—the former center of civilization in A Song of Ice and Fire’s developed world—be literally in the center of the world.

(Also, we’ll redo the calculations later with the equator as the southern edge of the map.)

We now have a useful grid that we can overlay on the Known World, but we need one more arbitrary line to put an outer bound on that grid before we can estimate how big the planet is. Since the Known World map shows us the Shivering Sea and the Land of Always Winter, let’s decide where this planet’s “Arctic” Circle will be.

On Earth, the Arctic Circle is a a little north of the 66th latitudinal parallel, and as you head north the ecosystem is primarily comprised of tundra, then treeless permafrost, then ice. Since the Arctic is marked for its lack of trees, we’ll put Planet Westeros’ “Arctic Circle” at the northern edge of the Haunted Forest beyond the Wall.

For the purposes of this speculation, I’m assuming that the amount of polar ice in the world is equivalent to the amount present in Earth’s pre-industrial society, barring any Little Ice Ages. How extended winters and summer would affect Ice Ages, coastlines, and climate on Planet Westeros is a fascinating tangent to think about, but not entirely relevant to determining the size of the planet.

So this is our map:

The distance between Planet Westeros’ “Arctic Circle” and equator is 4125 miles. On Earth, the distance between the Arctic circle and equator is 4608 miles (give or take).

If you accept the equator and “Arctic Circle” where they are, this means that the planet that Westeros is on is smaller than Earth! To put it in numbers, Planet Westeros is only 89.51% the size of Earth.

With this percentage in hand, we can now figure out just how much of the world is “known” in A Song of Ice and Fire.

But first, some incidental numbers: On Earth, the distance from the Arctic circle to the North Pole is 1600 miles (roughly). 89.51% of that is 1432.16 miles.

Dropping the .16 for the sake of some more straightforward whole numbers, this makes Planet Westeros 5557 miles from equator to pole, which equals 11,114 miles from pole to pole. Earth is 12,416 miles from pole to pole and its equatorial circumference is 24,901 miles. Since Planet Westeros is 89.51% the size of Earth, its circumference is most likely 22,289 miles (rounding up).

The Known World map is 8750 miles across by 5750 miles tall, depicting 50,312,500 square miles. On Earth, you’d be depicting 25.54% of the planet, but Planet Westeros is smaller, so the Known World map is actually depicting 28.54% of the planet that Westeros is on.

The Arctic takes up 8% of the Earth, so let’s double that for the South Pole and say that Planet Westeros has 84% of mappable and explorable land. We’ve seen 28.54% of it, which means over half of the planet that George R. R. Martin’s Song of Ice and Fire takes place on is still unexplored.

Lots of places for dragons and other terrors to hide, aren’t there?

Okay, as promised before, here’s how it works out if you put the equator at the bottom of the Known World map but keep the “Arctic Circle” line where it is.

If you move the equator south, that makes 4813 miles between Planet Westeros’ equator and its “Arctic Circle,” which makes the planet that Westeros is on 4.4% larger than Earth. That means the Known World map is depicting 24.4% of Planet Westeros.

So even if the planet that Westeros is on is actually larger than Earth, we still haven’t seen more than half of it!

A note on the calculations: Maps of spheres are tricky beasts, and spheres that get bulgy in the middle and flat on the top, like our awesome planet, are even trickier. In addition, the Song of Ice and Fire map of the Known World is a flat rectangular projection that is not a mercator projection, i.e. distance and land are not distorted as they travel away from the equator as they would be in a mercator. The two don’t quite fit together, so I kept the comparison between them simple (with the math remaining purely back-of-the-napkin). I still ended up with some surprising results, though! I’m curious what others might come up with in regards to size and area comparisons.